A transmitter comprises an analog-to-digital converter, an audio signal compressor, a framer, a scrambler, a modulator, and a transmitting unit. The analog-to-digital converter translates an analog audio signal into a digital Pulse-Code Modulation (PCM) format audio signal. The audio signal compressor compresses the PCM format audio signal into a coded bit stream with a modified Adaptive differential Pulse-code Modulation (ADPCM) algorithm. The framer packetizes the coded bit stream into a 1.125 ms frame data by adding a preamble, a signaling field, a data field, and a cyclic redundancy check field to the coded bit stream. The scrambler scrambles the frame data with an ID number. The modulator generates a modulated signal by modulating the scrambled frame data with a predetermined modulation scheme. The transmitting unit transmits the modulated signal.